Method and apparatus for selecting reference signal tones for decoding a channel

ABSTRACT

Methods and apparatuses are provided that include selecting reference signal (RS) or other tones to utilize in estimating a channel for decoding one or more channels. Where the RS tones are interfered by other base stations, interference cancelation can be performed over the RS tones. Since interference can vary over the tones, interference cancelation can yield RS tones of varying quality. Thus, a quality of each of the RS tones can be determined, and at least a subset of the RS tones can be selected for estimating a channel. Additionally or alternatively, the RS tones can be weighted or otherwise classified for performing channel estimation using the RS tones.

CLAIM OF PRIORITY UNDER 35 U.S.C. §119

The present application for patent is a divisional application ofNon-Provisional application Ser. No. 13/269,408 entitled “METHOD ANDAPPARATUS FOR SELECTING REFERENCE SIGNAL TONES FOR DECODING A CHANNEL”and filed on Oct. 7, 2011, which claims priority to ProvisionalApplication No. 61/474,699, entitled “METHOD AND APPARATUS FOR SELECTIVEREFERENCE SIGNAL USE IN PHYSICAL BROADCAST CHANNEL INTERFERENCECANCELATION” and filed on Apr. 12, 2011, assigned to the assignee hereofand hereby expressly incorporated by reference herein.

BACKGROUND

1. Field

The following description relates generally to wireless networkcommunications, and more particularly to using reference signals fordecoding communications.

2. Background

Wireless communication systems are widely deployed to provide varioustypes of communication content such as, for example, voice, data, and soon. Typical wireless communication systems may be multiple-accesssystems capable of supporting communication with multiple users bysharing available system resources (e.g., bandwidth, transmit power, . .. ). Examples of such multiple-access systems may include code divisionmultiple access (CDMA) systems, time division multiple access (TDMA)systems, frequency division multiple access (FDMA) systems, orthogonalfrequency division multiple access (OFDMA) systems, and the like.Additionally, the systems can conform to specifications such as thirdgeneration partnership project (3GPP) (e.g., 3GPP LTE (Long TermEvolution)/LTE-Advanced), ultra mobile broadband (UMB), evolution dataoptimized (EV-DO), etc.

Generally, wireless multiple-access communication systems maysimultaneously support communication for multiple mobile devices. Eachmobile device may communicate with one or more base stations viatransmissions on forward and reverse links. The forward link (ordownlink) refers to the communication link from base stations to mobiledevices, and the reverse link (or uplink) refers to the communicationlink from mobile devices to base stations. Further, communicationsbetween mobile devices and base stations may be established viasingle-input single-output (SISO) systems, multiple-input single-output(MISO) systems, multiple-input multiple-output (MIMO) systems, and soforth.

In addition, some wireless networks allow deployment of lower power basestations (e.g., femto nodes, pico nodes, micro nodes, etc.), to which adevice can connect to receive alternative wireless network access. Forexample, the lower power base station can communicate with the wirelessnetwork over a broadband or other backhaul connection (e.g., a digitalsubscriber line (DSL) connection, T1 connection, cable connection,etc.), while also providing an access link over which devices cancommunicate therewith to receive access to the wireless network. Lowerpower base stations can be deployed within macrocell base stationcoverage areas, and as such, in some examples, devices communicatingwith the lower power base station may have lower path loss than from amacrocell base station but may have lower received power than themacrocell base station due to stronger transmit downlink power from themacrocell base station. The device, however, may desire to communicateand/or establish connection with the lower power base station (e.g., toreceive additional services, increased data rate, or other factors thatcan improve overall system performance), in which case the macrocellbase station can cause interference to communications from the femtonode at the device.

SUMMARY

The following presents a simplified summary of one or more aspects inorder to provide a basic understanding of such aspects. This summary isnot an extensive overview of all contemplated aspects, and is intendedto neither identify key or critical elements of all aspects nordelineate the scope of any or all aspects. Its sole purpose is topresent some concepts of one or more aspects in a simplified form as aprelude to the more detailed description that is presented later.

In accordance with one or more aspects and corresponding disclosurethereof, the present disclosure describes various aspects in connectionwith canceling interference caused over a broadcast channel of a femtonode or similar lower power base station by another base station. Forexample, a device can obtain a plurality of reference signal (RS) tonesfrom a plurality of RSs of the femto node, and can modify the RS tonesto remove interference from one or more other base stations. The devicecan determine a quality associated with each of the RS tones, and candetermine at least a subset of the RS tones to utilize for estimating achannel based on the quality, from which a data channel can be decoded.For example, the device can experience different levels of interferenceover each of the plurality of RS tones, and thus determining the qualityof the RS tones after interference cancelation allows the device toutilize more favorable tones to estimate a channel for decoding the datachannel.

According to an example, a method of wireless communication is providedthat includes receiving a plurality of RS tones from a pluralityreference signals from a first base station, modifying the plurality ofRS tones to remove interference from at least another base station, anddetermining a quality of the plurality of RS tones as modified. Themethod further includes obtaining at least one channel estimate based onthe quality of the plurality of RS tones and decoding a data channel ofthe first base station based on the at least one channel estimate.

In another aspect, an apparatus for wireless communication is provided.The apparatus includes means for receiving a plurality of RS tones in aplurality reference signals from a first base station, means formodifying the plurality of RS tones to remove interference from at leastone other base station, and means for determining a quality of theplurality of RS tones as modified. The apparatus also includes means forobtaining at least one channel estimate of at least one data tone basedon the quality of the plurality of RS tones and means for decoding adata channel of the first base station based on the at least one channelestimate.

In yet another aspect, an apparatus for wireless communication isprovided including at least one processor configured to receive aplurality of RS tones in a plurality reference signals from a first basestation, modify the plurality of RS tones to remove interference from atleast one other base station, and determine a quality of the pluralityof RS tones as modified. The at least one processor is furtherconfigured to obtain at least one channel estimate of at least one datatone based on the quality of the plurality of RS tones and decode a datachannel of the first base station based on the at least one channelestimate. The apparatus further includes a memory coupled to the atleast one processor.

Still, in another aspect, a computer-program product for wirelesscommunication is provided including a computer-readable medium havingcode for causing at least one computer to receive a plurality of RStones in a plurality reference signals from a first base station, codefor causing the at least one computer to modify the plurality of RStones to remove interference from at least one other base station, andcode for causing the at least one computer to determine a quality of theplurality of RS tones as modified. The computer-readable medium furtherincludes code for causing the at least one computer to obtain at leastone channel estimate of at least one data tone based on the quality ofthe plurality of RS tones and code for causing the at least one computerto decode a data channel of the first base station based on the at leastone channel estimate.

According to an example, a method for muting tones at a first basestation to aid in decoding channels of a second base station in asubframe is provided that includes determining a location of one or moretones over which a base station transmits a reference signal and mutinga subset of tones corresponding to the location of the one or moretones.

In another aspect, an apparatus for muting tones at a first base stationto aid in decoding channels of a second base station in a subframe isprovided. The apparatus includes means for determining a location of oneor more tones over which a base station transmits a reference signal andmeans for muting a subset of tones corresponding to the location of theone or more tones.

In yet another aspect, an apparatus for muting tones at a first basestation to aid in decoding channels of a second base station in asubframe is provided including at least one processor configured todetermine a location of one or more tones over which a base stationtransmits a reference signal. The at least one processor is furtherconfigured to mute a subset of tones corresponding to the location ofthe one or more tones. The apparatus further includes a memory coupledto the at least one processor.

Still, in another aspect, a computer-program product for muting tones ata first base station to aid in decoding channels of a second basestation in a subframe is provided including a computer-readable mediumhaving code for causing at least one computer to determine a location ofone or more tones over which a base station transmits a referencesignal. The computer-readable medium further includes code for causingthe at least one computer to mute a subset of tones corresponding to thelocation of the one or more tones.

To the accomplishment of the foregoing and related ends, the one or moreaspects comprise the features hereinafter fully described andparticularly pointed out in the claims. The following description andthe annexed drawings set forth in detail certain illustrative featuresof the one or more aspects. These features are indicative, however, ofbut a few of the various ways in which the principles of various aspectsmay be employed, and this description is intended to include all suchaspects and their equivalents.

BRIEF DESCRIPTION OF THE DRAWINGS

The disclosed aspects will hereinafter be described in conjunction withthe appended drawings, provided to illustrate and not to limit thedisclosed aspects, wherein like designations denote like elements, andin which:

FIG. 1 is a block diagram of an aspect of a system for decoding basestation communications.

FIG. 2 is a block diagram of an aspect of a system for decodinginterference-canceled communications from a base station.

FIG. 3 is a block diagram of an aspect of a system for muting referencesignal (RS) tones used by a femto node.

FIG. 4 is a block diagram of example frame structures.

FIG. 5 is a flow chart of an aspect of a methodology for decoding abroadcast channel based on determining RS tone quality.

FIG. 6 is a flow chart of an aspect of weighting RS tones for decoding achannel.

FIG. 7 is a flow chart of an aspect of a methodology for classifying RStones for decoding a channel.

FIG. 8 is a flow chart of an aspect of a methodology for muting RS tonesused by a femto node.

FIG. 9 is a block diagram of an aspect of an example mobile device inaccordance with aspects described herein.

FIG. 10 is a block diagram of an aspect of an example system inaccordance with aspects described herein.

FIG. 11 is a block diagram of an aspect of a wireless communicationsystem in accordance with various aspects set forth herein.

FIG. 12 is a schematic block diagram of an aspect of a wireless networkenvironment that can be employed in conjunction with the various systemsand methods described herein.

DETAILED DESCRIPTION

Various aspects are now described with reference to the drawings. In thefollowing description, for purposes of explanation, numerous specificdetails are set forth in order to provide a thorough understanding ofone or more aspects. It may be evident, however, that such aspect(s) maybe practiced without these specific details.

Described further herein are various considerations related toestimating a channel of a femto node or other lower power base stationbased in part on a quality of interference-canceled reference signal(RS) tones. Though the aspects described herein often refer to a femtonode, it is to be appreciated that substantially any low power basestation can be used to perform functionality and achieve resultsdescribed herein, such as a home Node B or home eNode B (H(e)NB), a piconode, micro node, etc. For example, a device can decode a broadcastchannel of the macrocell base station using channel estimates from RSsreceived therefrom, and can cancel the broadcast channel of themacrocell base station by using channel estimates either from RSs, froma corresponding data region, or from both RSs and the data region. Thedevice can use the received signal after cancelation to obtain channelestimates for the weaker femto node from one or more RSs thereof, andcan perform decoding of a broadcast channel for the femto node using theinterference-canceled samples. The device, however, can experiencedifferent levels of interference from the macro node over the broadcastchannel and/or one or more RSs of the femto node.

In this regard, the device can determine a quality of theinterference-canceled samples, and can select samples (e.g., tones) toutilize in performing a channel estimate of the broadcast channel of thefemto node. For example, the device can select samples having a highestmeasured quality metric (e.g., SNR) before or after canceling theinterference. In another example, the device can determine quality ofthe samples based in part on a channel partitioning between the femtonode and the macrocell base station (e.g., select RS samples based onwhether they are in a PBCH region, a control region, a data region,etc.). In yet another example, the device can determine a quality of thesamples based in part on a measured power of the samples, frequencyoffset, rate of change or channel variation, and/or other considerationsdescribed further herein. Moreover, the device can alternatively weightand/or classify samples to use in performing the channel estimationaccording to the foregoing considerations. In this regard, reliabilityof decoding of the broadcast channel of a femto node can be improvedbased on using desirable RS samples in performing channel estimation fordecoding the channel.

As used in this application, the terms “component,” “module,” “system”and the like are intended to include a computer-related entity, such asbut not limited to hardware, firmware, a combination of hardware andsoftware, software, or software in execution, etc. For example, acomponent may be, but is not limited to being, a process running on aprocessor, a processor, an object, an executable, a thread of execution,a program, and/or a computer. By way of illustration, both anapplication running on a computing device and the computing device canbe a component. One or more components can reside within a processand/or thread of execution and a component may be localized on onecomputer and/or distributed between two or more computers. In addition,these components can execute from various computer readable media havingvarious data structures stored thereon. The components may communicateby way of local and/or remote processes such as in accordance with asignal having one or more data packets, such as data from one componentinteracting with another component in a local system, distributedsystem, and/or across a network such as the Internet with other systemsby way of the signal.

Furthermore, various aspects are described herein in connection with aterminal, which can be a wired terminal or a wireless terminal. Aterminal can also be called a system, device, subscriber unit,subscriber station, mobile station, mobile, mobile device, remotestation, remote terminal, access terminal, user terminal, terminal,communication device, user agent, user device, or user equipment (UE),etc. A wireless terminal may be a cellular telephone, a satellite phone,a cordless telephone, a Session Initiation Protocol (SIP) phone, awireless local loop (WLL) station, a personal digital assistant (PDA), ahandheld device having wireless connection capability, a computingdevice, a tablet, a smart book, a netbook, or other processing devicesconnected to a wireless modem, etc. Moreover, various aspects aredescribed herein in connection with a base station. A base station maybe utilized for communicating with wireless terminal(s) and may also bereferred to as an access point, a Node B, evolved Node B (eNB), or someother terminology.

Moreover, the term “or” is intended to mean an inclusive “or” ratherthan an exclusive “or.” That is, unless specified otherwise, or clearfrom the context, the phrase “X employs A or B” is intended to mean anyof the natural inclusive permutations. That is, the phrase “X employs Aor B” is satisfied by any of the following instances: X employs A; Xemploys B; or X employs both A and B. In addition, the articles “a” and“an” as used in this application and the appended claims shouldgenerally be construed to mean “one or more” unless specified otherwiseor clear from the context to be directed to a singular form.

The techniques described herein may be used for various wirelesscommunication systems such as CDMA, TDMA, FDMA, OFDMA, SC-FDMA and othersystems. The terms “system” and “network” are often usedinterchangeably. A CDMA system may implement a radio technology such asUniversal Terrestrial Radio Access (UTRA), cdma2000, etc. UTRA includesWideband-CDMA (W-CDMA) and other variants of CDMA. Further, cdma2000covers IS-2000, IS-95 and IS-856 standards. A TDMA system may implementa radio technology such as Global System for Mobile Communications(GSM). An OFDMA system may implement a radio technology such as EvolvedUTRA (E-UTRA), Ultra Mobile Broadband (UMB), IEEE 802.11 (Wi-Fi), IEEE802.16 (WiMAX), IEEE 802.20, Flash-OFDM®, etc. UTRA and E-UTRA are partof Universal Mobile Telecommunication System (UMTS). 3GPP Long TermEvolution (LTE) is a release of UMTS that uses E-UTRA, which employsOFDMA on the downlink and SC-FDMA on the uplink. UTRA, E-UTRA, UMTS,LTE/LTE-Advanced and GSM are described in documents from an organizationnamed “3rd Generation Partnership Project” (3GPP). Additionally,cdma2000 and UMB are described in documents from an organization named“3rd Generation Partnership Project 2” (3GPP2). Further, such wirelesscommunication systems may additionally include peer-to-peer (e.g.,mobile-to-mobile) ad hoc network systems often using unpaired unlicensedspectrums, 802.xx wireless LAN, BLUETOOTH and any other short- orlong-range, wireless communication techniques.

Various aspects or features will be presented in terms of systems thatmay include a number of devices, components, modules, and the like. Itis to be understood and appreciated that the various systems may includeadditional devices, components, modules, etc. and/or may not include allof the devices, components, modules etc. discussed in connection withthe figures. A combination of these approaches may also be used.

FIG. 1 illustrates an example system 100 for communicating with a basestation when interfered by at least another base station. System 100includes a device 102 that communicates with base station 104. Signalsreceived from base station 104, for example, can be interfered bysignals transmitted by base station 106 over a similar frequencyspectrum in similar time periods. Device 102 can be a UE, a modem (orother tethered device), a portion thereof, and/or the like. Basestations 104 and 106 can each be a macrocell base station, a femto node,pico node, micro node, or other low power base station, a relay, amobile base station, a device (e.g., communicating in peer-to-peer orad-hoc mode), a portion thereof, and/or the like.

In some network deployments, for example, device 102 can communicatewith base station 104 though base station 104 exhibits a lower receivedsignal power at device 102 than base station 106. For example, in aheterogeneously deployed network comprising femto nodes, where basestation 104 is a femto node, device 102 can communicate with basestation 104 while base station 106 can be a macrocell base stationoffering an improved signal quality over base station 104. Base station104, however, can provide additional services, improved bandwidthcapabilities, improved network performance due to cell splitting gainswith range expansion and resource partitioning, and/or otherconsiderations, such that device 102 can prefer to communicate with basestation 104 over base station 106 where possible. Thus, where channelstransmitted by base station 104 are interfered by base station 106,device 102 can remove the interference from base station 106 to processchannels from base station 104.

For example, where base stations 104 and 106 operate using a similarnetwork technology, the base stations 104 and 106 can overlap channeltransmissions. Thus, device 102 can estimate a channel of base station106 in a received signal that interferes with a similar desired channelof base station 104. The device 102 can then decode the channel frombase station 106 based on the channel estimate and cancel the channelfrom the signal. The device 102 can use the resulting signal to obtainchannel estimates for decoding a similar channel communicated by basestation 104. The device 102 can utilize RS tones in the signal toperform the channel estimations.

For example, a tone can refer to a portion of frequency over the symbolin a portion of time. In one example, device 102 and base stations 104and 106 can communicate using orthogonal frequency division multiplexing(OFDM) having a frame including one or more subframes where eachsubframe can include a number of OFDM symbols. The OFDM symbols cancorrespond to time periods within the subframe. In addition, each OFDMsymbol can be divided into a number of tones (or subcarriers) of anoperating frequency such that each tone can be utilized to transmit atleast a portion of a signal. In addition, certain symbols and/or tonescan be reserved for specific purposes. In one example, a broadcastchannel region is defined as one or more symbols, and each of basestation 104 and 106 can use the tones within the region for transmittingsignals corresponding to the broadcast channel.

Base station 104 can transmit various RS tones that can be utilized forperforming channel estimation of other channels transmitted by basestation 104. Depending on where the RS tones are transmitted, the device102 can experience varying levels of interference from base station 106.For example, where RS tones from base station 104 are transmitted in thebroadcast channel region, the RS tones can be interfered by broadcastchannel transmissions from base station 106. The device 102 can decodethe broadcast channel of the base station 106 based on RS tones of thebase station 104, and can cancel the broadcast channel from the RS tonesin the broadcast channel region. Where the base station 104 transmits RStones in other regions, however, the RS tones may be interfered by RSsfrom base station 106, data from base station 106, and/or the like. Inthese cases, the level of interference over given RS tones may not beconsistent, and thus, interference cancelation may not be as accurateupon canceling the broadcast channel of base station 106.

Thus, device 102 can determine a quality of one or more RS tonesreceived from base station 104 after canceling interference from basestation 106. Device 102 can select a portion of the one or more RS toneshaving at least a threshold quality to perform channel estimations fordecoding a broadcast channel or other channels of base station 104. Inanother example, device 102 can assign weights to the RS tonescorresponding to the quality, and can thus utilize higher quality RStones with a higher weight to decode the broadcast channel, whileplacing less consideration on RS tones with a lower weight. Device 102can determine the quality of the RS tones based on at least one ofsignal measurements of the RS tones (e.g.,signal-to-interference-and-noise ratio (SINR)), determining a channelpartitioning between base stations 104 and 106, determining whether RStransmissions of base station 104 and 106 are colliding or non-collidingover the RS tones, determining a power utilized to transmit the RStones, power levels received on the RS tones, and/or the like. Moreover,in one example, device 102 can determine an interference estimate overdata tones, or at least a subset of the RS tones, or both and can decodethe broadcast channel of base station 104 based also in part on theinterference estimate.

FIG. 2 illustrates an example apparatus 200 for decoding channels fromone or more base stations. Apparatus 200 can be a device, such as device102, that communicates with one or more base stations in a wirelessnetwork to receive access thereto, and can include additional modulesthan those depicted. Apparatus 200 can include a receiving module 202for receiving signals transmitted by one or more base stations, aninterference canceling module 204 for removing interference from thesignals caused by one or more base stations, and an optional toneselecting module 206 for selecting one or more tones of the signals fromwhich to perform channel estimation. Apparatus 200 also includes achannel estimating module 208 for performing channel estimation overportions of the signals with interference removed, and a channeldecoding module 210 for obtaining channel information based on thechannel estimates. Apparatus 200 can optionally include a tone weightingmodule 212 for assigning weights to one or more tones for performingchannel estimates, and/or an interference estimating module 214 forperforming interference estimation of at least a subset of the tones touse in decoding the channel information.

According to an example, receiving module 202 can obtain signals with RStones and channel information from a plurality of base stations (e.g., afemto node and an interfering macrocell base station). Interferencecanceling module 204 can determine interference from the signals andcancel the interference. In one example, interference canceling module204 can determine one or more RS tones received from the macrocell basestation, and can utilize the tones to perform a channel estimation on abroadcast channel (e.g., primary broadcast channel (PBCH) in LTE) of themacrocell base station. Interference canceling module 204 can decode thebroadcast channel based on the channel estimates, and can cancel thebroadcast channel and RS tones from the signals to yield a signal fromthe femto node.

Tone selecting module 206 can determine a plurality of RS tones in theresulting signals. As described, since the RS tones can have beeninterfered by macrocell base station communications at different levels,depending on the location of the RS tones within a frame andcommunication properties of the macrocell base station within the frame,some of the interference-canceled RS tones can exhibit a higher quality(e.g., SINR) than others (e.g., tones from which interference could notbe canceled). Thus, tone selecting module 206 can determine a quality ofthe RS tones and can select a portion of the RS tones for performingchannel estimation over one or more signals received from the femtonode. Channel estimating module 208 can utilize the selected portion ofthe RS tones in channel estimation to produce one or more data tones,and channel decoding module 210 can decode one or more channels, such asa broadcast channel (e.g., PBCH), data channel (e.g., PDSCH), or otherchannel of interest of the femto node to produce the decoded channelinformation. Channel decoding module 210 can utilize the channelinformation to process other channels received from the femto node, inone example.

In an example, tone selecting module 206 can obtain one or moreparameters for determining which tones to select. For instance, toneselecting module 206 can obtain information regarding channelpartitioning to determine whether certain RS tones are in certainchannel regions (e.g., a control channel region, a data channel region,a broadcast channel region, etc.). As described, the macrocell basestation and femto node can utilize similar channel structures, and thus,tone selecting module 206 can utilize preconfigured channelconfigurations to determine channel regions of related RS tones. Inanother example, tone selecting module 206 can receive the channelpartitioning information from one or more network components, themacrocell base station and/or femto node, etc. The tone selecting module206 can obtain information about resource partitioning between themacrocell base station and femto node, which the tone selecting module206 can use to determine the interference caused to RS and datatransmission from the femto node to the device. For example, theresource partitioning information can include determining whichsubframes are used by the macrocell base station to transmit data and/orcontrol data, which subframes are used as multimedia broadcast oversingle frequency network (MBSFN) subframes or almost blank subframes(ABS) by macrocell base stations, and/or the like.

In either case, in an example, tone selecting module 206 can at leastdetermine to select the RS tones that are in a broadcast channel region(e.g., PBCH) to use for performing channel estimation for at least abroadcast channel of the femto node. For example, interference can moreeasily be canceled over RS tones in the broadcast channel region sincethe decoded signal from the macrocell base station used to cancelinterference is in the same broadcast channel region. Thus, theinterference cancelation can be accurate in this region, and the RStones of the femto node can be of a higher quality than other RS tonesafter the interference cancelation. In other examples, tone selectingmodule 206 can define different filtering parameters for selecting RStones within certain channel regions (e.g., a set of filteringparameters for selecting RS tones in a broadcast channel region and adifferent set of filtering parameters for selecting RS tones in a datachannel region).

Moreover, for example, tone selecting module 206 can additionally obtaina power of the one or more RS tones. In one example, tone selectingmodule 206 can compute P1, which can be a power of one or more RS tonesas received in a control channel region (e.g., physical downlink controlchannel (PDCCH)), P2, which can be a power of one or more RS tones asreceived in a data channel region (e.g., physical downlink sharedchannel (PDSCH)) but not a broadcast channel region (e.g., PBCH), and P,which can be a power of one or more RS tones as received in a datachannel region (e.g., PDSCH) and in the PBCH region. In this example,tone selecting module 206 can select RS tones in the control channelregion if P1-P is less than a threshold level (e.g., three or sixdecibels (dB)). Also, in this example, tone selecting module 206 canselect RS tones in the data region if P2-P is less than a thresholdlevel (e.g., three or six dB).

Tone selecting module 206 can recompute P1, P2, and P when a basestation signal is decoded and canceled and/or before performinginterference cancelation. It is to be appreciated that P1 and P2 areseparately computed since the control channel region may be lightlyloaded by the macrocell base station and/or other base stations, suchthat the corresponding RS tones from the femto node may have a signalquality above a threshold. Alternately, the control channel region maybe loaded but signals from the macrocell base station may be outside ofa center frequency range (e.g., six resource blocks), and thus the RStones of the femto node may similarly have a signal quality above athreshold.

In another example, tone selecting module 206 can select RS tones basedon whether the RS tones of the femto node collide with those of themacrocell base station, which tone selecting module 206 can determinebased on cell identifiers of the femto node and macrocell base station.In other examples, tone selecting module 206 can use other parameters,such as a frequency offset. In this example, the frequency offset can bereceived from one or more network components, and where the frequencyoffset is large (e.g., above a threshold), tone selecting module 206 canselect the RS tones near the data or related channel of interest (e.g.,in frequency and/or time) while including RS tones that are further away(e.g., based in part on a distance in the time domain) where thefrequency offset is small.

In an additional example, tone selecting module 206 can similarly selectRS tones based on a determined rate of channel variation of a wirelesschannel at the apparatus 200 where above, below, or at a threshold. Forexample, this can include using more RS tones that are separated (e.g.,the in time domain or filtering) such RS tones resulting in moreaveraging over time when the rate of variation is low, while using RStones nearer to the data or related channel of interest (e.g., infrequency or time) or using filtering parameters that lead to lessaveraging over time when rate of variation is high. Moreover, forexample, tone selecting module 206 can select different sets of RS tonesfor multiple different channel estimates by channel estimating module208, and channel decoding module 210 can utilize the multiple channelestimates in decoding the broadcast channel of the femto node.

In further examples, tone selecting module 206 can determine a qualityof the RS tones based on whether a signal is canceled from the RS tonesby interference canceling module 204. In one example, an indication ofsuch can be received from the interference canceling module 204. Toneselecting module 206 can assign a better quality to those RS tones overwhich a signal is canceled. In another example, tone selecting module206 can determine a quality of the RS tones based on whether a signal istransmitted over the RS tones by other base stations. Such RS tones canbe of lower quality than those over which signals are not transmitted byother base stations. In one example, tone selecting module 206 candetermine whether other base stations transmit over the RS tones basedon a resource partitioning thereof, a MBSFN/ABS configuration of theother base station, a received power comparison over the plurality of RStones with the interference-canceled RS tones, interference canceleddata tones, or other tones that are known to not have interference fromthe macrocell base station (e.g., null tones in the PBCH region of themacrocell base station, tones where the macrocell base station is nottransmitting in a ABS/MBSFN configuration, null tones corresponding toreference signal of a second antenna port on first OFDM symbol of eachsubframe where the macrocell base station uses a single common referencesignal (CRS) port, etc.), and/or the like.

In another example, tone weighting module 212 can utilize similarparameters described above to assign a weight to, or otherwise classify,the RS tones. In this example, tone weighting module 212 can assignweights as a function of the parameters, according to variousthresholds, and/or the like. In a specific example, tone weightingmodule 212 can assign a highest available weight to RS tones from thefemto node in the broadcast channel regions, a lower weight to RS tonesin a data or control channel region according to the P1, P2, and/or Pparameter values, frequency offset, rate of channel variation etc.Channel estimating module 208 can utilize the RS tones according to theassigned weight to determine the channel estimates. For example, channelestimating module 208 can apply the weight to the RS tones whileaveraging to obtain channel estimates from the RS tones. In one example,channel estimating module 208 can classify the RS tones according toweight (e.g., high quality, low quality, middle, quality, etc.), and canperform at least one channel estimate for RS tones having a similarclassification. Channel estimating module 208 can perform additionalchannel estimations for RS tones having different classifications, andchannel decoding module 210 can decode the channel from the femto nodeusing the multiple channel estimates.

In another example, where tone weighting module 212 classifies the RStones, channel estimating module 208 can perform multiple channelestimates using different combinations of the classifications to derivea substantially accurate channel estimate. In one example, toneweighting module 212 can classify RS tones from the femto node into atleast two groups: a more desirable group and a less desirable group(e.g., based on quality of the RS tones). In this example, channelestimating module 208 can attempt to estimate the channel, and channeldecoding module 210 can decode the channel using the estimate. If thedata decoding is successful (e.g., a cyclic redundancy check (CRC)passes) then it is likely that the channel estimation was reasonablyaccurate. If the channel estimation is not determined to besubstantially accurate based on the verification, channel estimatingmodule 208 can perform an additional channel estimate using tones fromthe more desirable group along with one or more tones from the lessdesirable group, and proceed to data decoding and so on, until at leastone of a channel estimation is achieved that results in successfuldecoding, or other stopping criteria are met, such as attempting acertain number of combinations of channel estimates.

For example, for four RS tones, where two are in the more desirablegroup and two are in the less desirable group, the channel estimatingmodule 208 can attempt channel estimation with the two from the moredesirable group alone. If the channel estimation is not substantiallyaccurate, the channel estimating module 208 can attempt channelestimation with the two from the more desirable group, and one tone fromthe less desirable group. If the channel estimation is still notsubstantially accurate, the channel estimating module 208 can attemptchannel estimation with the two from the more desirable group, and theother tone from the less desirable group. If the channel estimation isstill not substantially accurate, the channel estimating module 208 canattempt channel estimation with the two from the more desirable group,and the two tones from the less desirable group, etc.

In another example, channel decoding module 210 can also use aninterference estimate in addition to a channel estimate to decode thechannel. In one example, interference estimating module 214 can performthe interference estimate using RS tones on the resource block in whichthe data is located, as it can be assumed that the RS tones in thatresource block see the same interference as the data. When cancelinginterference (e.g., PBCH cancelation and/or CRS cancelation), however,the data channel region may not have interference from the macrocellbase station. Thus, some RS tones may continue to be interfered from thedata of the macrocell base station that is not canceled, while other RStones may not be interfered by the macrocell base station. In thisregard, interference estimating module 214 can determine to estimateinterference over at least a subset of RS tones that are not interferedby the macrocell base station. For example, the interference estimatingmodule 214 can identify such RS tones as described with respect to toneselecting module 206 (e.g., resource partitioning information, MBSFN/ABSconfiguration, power measurements, etc.). In addition, interferenceestimating module 214 can perform interference estimates in part byusing the covariance of data tones directly. The covariance of the datatones can provide the signal plus noise power. Since PBCH is designed tobe decoded at low SNR, however, when the SNR is low, the signal power isnegligible and hence interference estimate can be substantially equal tothe desired noise power. When the SNR is high, PBCH can likely bedecoded even with incorrect estimate of interference.

Moreover, for example, interference estimating module 214 can determineat least a subset of the plurality of RS tones for performinginterference estimation based on at least one of a primarysynchronization signal (PSS) received from the femto node or macrocellbase station, a resource partitioning between the macrocell base stationand the femto node, whether a subframe over which the plurality of RStones are received is a MBSFN/ABS subframe, etc. Moreover, for example,interference estimating module 214 can determine the RS tones based inpart on a received power comparison between at least one of theplurality of RS tones and an interference-canceled tone or data tone, orother tones that are known to not have interference from the macrocellbase station (e.g., null tones in the PBCH region of the macrocell basestation, tones where the macrocell base station is not transmitting in aABS/MBSFN configuration, etc.). In one example, a location of such tonescan be received from the macrocell base station, from one or morenetwork components, from a hardcoding or configuration, and/or the like.In another example, both interference estimating via RS tones and datatones can be used by channel decoding module 210 to decode the broadcastchannel in addition or alternatively to the channel estimates.

FIG. 3 illustrates an example apparatus 300 for transmitting broadcastsignals. Apparatus 300 can be a femto node, macrocell base station, orother base stations (e.g., base stations 104 and 106), that cancommunicate with devices in a wireless network to provide accessthereto. Apparatus 300 can include an optional RS location receivingmodule 302 for obtaining a RS locations used by weaker cells, ascheduling module 304 for scheduling resources for transmitting one ormore channels using one or more signals, and a transmitting module 306for transmitting data according to the scheduling.

According to an example, scheduling module 304 can determine whether tomute (e.g., not schedule transmissions over) tones utilized fortransmitting broadcast channel signals by femto nodes or other basestations to allow for decoding such channels without interference atdevices. This can be done over substantially all or at least a subset oftransmission opportunities within the broadcast channel region. Inanother example, RS location receiving module 302 can obtain informationregarding RS tone locations over which one or more neighboring femtonodes transmit RSs in the broadcast channel region, and schedulingmodule 304 can then mute some portion of the RS tone locations.

For example, RS location receiving module 302 can identify RS tones fromthe femto node or other network components in a subset of subframes, andcan determine a location of the tones in frequency and/or time. In anycase, scheduling module 304 can mute tones in the location of at least asubsequent subframe. For example, in an orthogonal frequency divisionmultiplexing (OFDM) configuration, RS location receiving module 302 canidentify the tone locations within one or more OFDM symbols in a givensubframe (e.g., based on signals received from the femto node, anindicated configuration, etc.), and scheduling module 304 can mute thetone locations in the OFDM symbols of a subsequent subframe. In anotherexample, the RS location receiving module 302 can determine locations ofthe tones in subsequent subframes based on the determined location andone or more hopping patterns used by the femto node (e.g., which can beindicated to or otherwise known by the apparatus 300). In any case,transmitting module 306 can transmit over tones scheduled by schedulingmodule 304, while refraining from transmitting over tone locations mutedby scheduling module 304. In one example, the muting can further includemuting RS tones over a portion of resource blocks in a subframe (e.g., acenter six or other number of resource blocks on a subset of OFDMsymbols that correspond to the RS tones).

FIG. 4 is a diagram illustrating example frame structures 400 and 402including resource element (e.g., tone) allocations for CRS and PBCH. Itis to be appreciated, however, that other frame structure can be used inaspects described herein. The PBCH payload can include 24 bits, with atail-biting convolution code with a ⅓ rate. The payload can change every40 milliseconds (ms) (e.g., changing with single frequency network (SFN)increments), and four redundancy versions (RV) can be transmitted withthe 40 ms. RV detection provides two least significant bits (LSB) ofSFN.

Within a subframe 404, the central resource blocks (e.g., center 6resource blocks (RB)) can be used for PBCH 406 transmissions. Exampleframe structures 400 depict various frame structures that differ basedin part on the number of CRSs ports used in communications. For example,a single port transmission 408 may include one CRS 414 port, a spacefrequency block coding (SFBC) 410 may include use two CRS 414 ports, anda SFBC frequency shift time diversity (FSTD) 412 may use four CRS 414ports. Additionally, resource elements (RE) may be used forcommunication of the PBCH 406, and as null tones 416.

As noted above, during interference cancelation, different RSs mayexperience different levels of interference depending on a number offactors. In one aspect, where a macrocell base station and femto nodecompletely collide, substantially all RSs may experience similar levelsof interference. For instance, if there are two cells that have RSs 414that completely collide, when interference cancelation is performed, thePBCH and RS of the stronger cell are canceled equally for substantiallyall RS 414 tones of the weaker cell, and as such, substantially all RSs414 may experience similar reduced interference.

In another aspect, a strong cell may provide a blank or almost blanksubframe, such as during resource partitioning, and may be configuredsuch that the two cells RSs do not collide. As such, before PBCH and RSinterference cancelation of the strong cell, RS 414 of the weaker cellcan be clean in the control region and the non-PBCH region (e.g.,outside of PBCH region 406), but may see interference from the PBCH ofthe stronger cell in the PBCH region (e.g., unless the CRS of weakercell happens to be in the null tones 416 of the stronger cell). Afterinterference cancelation of the strong cell PBCH, substantially all weakcell RSs 414 may experience similar reduced interference.

In another aspect, a strong cell may transmit using a regular subframeincluding data and may be configured such that the two cells RSs do notcollide. As such, before PBCH and RS interference cancelation of thestrong cell, the RS 414 of the weaker cell may experience stronginterference in the control region, the data region, and the PBCH region406. Although, in the PBCH region 406, the RSs 414 b may not experiencehigh interference if RS 414 b of weaker cell happens to be in the nulltones 416 of stronger cell. After PBCH IC and RS IC, RS 414 b in thePBCH region experiences relatively less interference from the strongcell than RS 414 a in data and control region.

In one aspect, where frequency offset information for the strong andweak cells is not available, the channel information from RS tones onthe different OFDM symbols may not be matched with the channel in PBCHregion. In such an aspect, use of RS tones 414 b close to the PBCHregion and/or in the PBCH region may result in more effective channelestimation than using all RS 414 tones. Thus, as described herein, adevice can associate RS tones 414 b with a higher quality and can selectthese tones for performing channel estimation. In other examples, thedevice can assign RS tones 414 b higher weight, a more desirableclassification, etc., based on determining a quality of the RS tones 414b (e.g., based on resource partitioning, a received power of the tones,etc.).

In example frame structures 402, different RB designs 418, 420, and 422may differ in CRS 424 and null tone 426 positioning, with respect to thePBCH 428. In operation, differing CRS 424 placement may result indiffering levels of interference observed after PBCH interferencecancelation and RS interference cancelation. For example, if both astrong cell and a weak cell are using RB 418 design, then the RSscollide and interference cancelation allows the weak cell RS to berecovered with minimal interference. By contrast, if a strong cell and aweak cell are using different RB designs (e.g., 418 and 420), then theweak cell RS tones may experience different levels of interference, asdiscussed above. Thus, a device can select, weight, classify, etc. tonesfor using in channel estimation.

FIGS. 5-8 illustrate example methodologies relating to decodingcommunications from one or more base stations. While, for purposes ofsimplicity of explanation, the methodologies are shown and described asa series of acts, it is to be understood and appreciated that themethodologies are not limited by the order of acts, as some acts may, inaccordance with one or more embodiments, occur concurrently with otheracts and/or in different orders from that shown and described herein.For example, it is to be appreciated that a methodology couldalternatively be represented as a series of interrelated states orevents, such as in a state diagram. Moreover, not all illustrated actsmay be required to implement a methodology in accordance with one ormore embodiments.

FIG. 5 depicts an example methodology 500 for decoding a broadcastchannel. At 502, a plurality of RS tones from a plurality of RSs can bereceived from a first base station. For example, the first base stationcan transmit one or more RSs to facilitate channel estimation anddecoding, and the RSs can be received over a related frequency spectrum.In addition, as described, the first base station can utilize OFDM orsimilar multiplexing over frequency and time to yield a plurality oftones over which the RSs can be transmitted in a given subframe.

At 504, the plurality of RS tones can be modified to remove interferencefrom at least another base station. Interference cancelation can beapplied to the tones in part by obtaining RS tones related to the atleast another base station and decoding a broadcast channel thereofbased on the RS tones. The signals from the at least another basestation can then be canceled by removing the decoded broadcast channelof the at least another base station from the received signals (e.g.,including the received RS tones thereof).

At 506, a quality of the RS tones as modified can be determined. Thiscan include, for example, obtaining a SINR of the RS tones, inferring aquality based on channel partitioning, RS power, frequency offset, etc.,as described above. In one specific example, the quality of the RS tonescan be determined by computing or otherwise determining a power thereof,and comparing the powers based on a location of the RS tones within oneor more channel regions to determine whether the RS tones are ofsufficient quality for channel estimation.

At 508, at least one channel estimate can be obtained based on thequality of the plurality of RS tones. RS tones of a quality at least ata threshold level can be utilized to estimate the channel. As described,RS tones in a broadcast channel region can be associated with a highquality sufficient to utilize the RS tones in estimating the channelsince a level of interference is readily attainable, such as to allowfor substantially accurate interference cancelation. Additional RS tonescan be associated with a high enough quality, as well as based on theconsiderations described above.

At 510, a data channel of the first base station can be decoded based onthe at least one channel estimate. Since interference can vary across RStones, using RS tones of a sufficient quality allows for improvedchannel estimating. In addition, interference estimates can be performedover the RS tones to assist in decoding the broadcast channel. The datachannel can correspond to a broadcast channel, in one example.

FIG. 6 depicts an example methodology 600 for decoding a broadcastchannel. At 602, a plurality of RS tones from a plurality of RSs can bereceived from a first base station. For example, the first base stationcan transmit one or more RSs to facilitate channel estimation anddecoding, and the RSs can be received over a related frequency spectrum.In addition, as described, the first base station can utilize OFDM orsimilar multiplexing over frequency and time to yield a plurality oftones over which the RSs can be transmitted in a given subframe.

At 604, the plurality of RS tones can be modified to remove interferencefrom at least another base station. Interference cancelation can beapplied to the tones in part by obtaining RS tones related to the atleast another base station and decoding a broadcast channel thereofbased on the RS tones. The signals from the at least another basestation can then be canceled by removing the decoded broadcast channelof the at least another base station from the received signals (e.g.,including the received RS tones thereof).

At 606, a quality of the RS tones as modified can be determined. Thiscan include, for example, obtaining a SINR of the RS tones, inferring aquality based on channel partitioning, RS power, frequency offset, etc.,as described above. In one specific example, the quality of the RS tonescan be determined by computing or otherwise determining a power thereof,and comparing the powers based on a location of the RS tones within oneor more channel regions to determine whether the RS tones are ofsufficient quality for channel estimation.

At 608, a weight can be assigned to the plurality of RS tones based inpart on the quality. In one example, the assigned weight can be afunction of the quality of the RS tones. As described, RS tones in abroadcast channel region can be assigned a higher weight at least sincea level of interference is readily attainable in this region such toallow for substantially accurate interference cancelation. Additional RStones can be assigned weights based on the considerations describedabove.

At 610, a channel of the first base station can be estimated using atleast a portion of the RS tones based on the weights. Since interferencecan vary across RS tones, as described, using RS tones with similarweights to estimate the channel and/or weighting the estimate based onthe weights of the RS tones used can provide a more accurate estimation.

FIG. 7 shows an example methodology 700 for estimating a channel usingcombinations of received RS tones. At 702, a plurality of RS tones canbe received from a plurality of reference signals from a first basestation. For example, the first base station can transmit one or moreRSs to facilitate channel estimation and decoding, and the RSs can bereceived over a related frequency spectrum. In addition, as described,the first base station can utilize OFDM or similar multiplexing overfrequency and time to yield a plurality of tones over which the RSs canbe transmitted in a given subframe.

At 704, the plurality of RS tones can be modified to remove interferencefrom at least another base station. Interference cancelation can beapplied to the tones in part by obtaining RS tones related to the atleast another base station and decoding a broadcast channel thereofbased on the RS tones. The signals from the at least another basestation can then be canceled by removing the decoded broadcast channelof the at least another base station from the received signals (e.g.,including the received RS tones thereof).

At 706, the RS tones can be classified based on a quality thereof. Thequality can be determined as described (e.g., based on obtaining a SINRof the RS tones, inferring a quality based on channel partitioning, RSpower, frequency offset, etc.). RS tones can be assigned aclassification based on comparing the determined qualities to certainthresholds. In one classification, the RS tones can be classified into agroup of more desirable tones and a group of less desirable tones, asdescribed.

At 708, the channel can be estimated based on a combination ofclassified RS tones. For example, the combination can be determinedbased on quality (e.g., a combination of the more desirable tones). Theestimate can be verified at 710 to determine whether the estimate isgood; for example, this can be based on comparing the estimate to a CRCto determine whether the estimate is at least at a threshold accuracy.If so, at 712, a data channel of the first base station can be decodedbased on the channel estimate.

If the estimate is not good (e.g., not at the threshold accuracy) at710, it can be determined at 714 whether combinations remain. Forexample, assuming four possible RS tones, with two having a moredesirable classification, there are four possible combinations toanalyze: (i) using the two desirable tones; (ii) using the two toneswith one less desirable tone; (iii) using the two tones with the otherless desirable tones; or (iv) using all four tones, etc. If combinationsremain, the channel can be estimated based on another combination ofclassified RS tones at 708. If no combinations remain, a broadcastchannel of the first base station can be decoded at 712 based on atleast one of the channel estimates.

FIG. 8 illustrates an example methodology 800 for muting RS tones usedby a femto node. At 802, a location one or more tones over which a basestation transmits an RS can be determined. This can include receivingsuch information from the base station (e.g., over a backhaul link), amobile device, or another network component, inferring the tones basedin part on receiving the RSs from the base station in at least a subsetof one or more other subframes, etc.

At 804, a subset of tones corresponding to the location of the one ormore tones can be muted. For example, a scheduler can ensure that nosignals are scheduled for transmission over the muted tones. This can bein a subsequent subframe, in substantially all subframes, and/or thelike, to allow devices to properly decode signals from the base station.

It will be appreciated that, in accordance with one or more aspectsdescribed herein, inferences can be made regarding determining a set ofRS tones for estimating a channel, and/or the like, as described. Asused herein, the term to “infer” or “inference” refers generally to theprocess of reasoning about or inferring states of the system,environment, and/or user from a set of observations as captured viaevents and/or data. Inference can be employed to identify a specificcontext or action, or can generate a probability distribution overstates, for example. The inference can be probabilistic—that is, thecomputation of a probability distribution over states of interest basedon a consideration of data and events. Inference can also refer totechniques employed for composing higher-level events from a set ofevents and/or data. Such inference results in the construction of newevents or actions from a set of observed events and/or stored eventdata, whether or not the events are correlated in close temporalproximity, and whether the events and data come from one or severalevent and data sources.

FIG. 9 is an illustration of a mobile device 900 that facilitatesdecoding a channel using one or more RS tones. Mobile device 900comprises a receiver 902 that receives a signal from, for instance, areceive antenna (not shown), performs typical actions on (e.g., filters,amplifies, downconverts, etc.) the received signal, and digitizes theconditioned signal to obtain samples. Receiver 902 can comprise ademodulator 904 that can demodulate received symbols and provide them toa processor 906 for channel estimation. Processor 906 can be a processordedicated to analyzing information received by receiver 902 and/orgenerating information for transmission by a transmitter 908, aprocessor that controls one or more components of mobile device 900,and/or a processor that both analyzes information received by receiver902, generates information for transmission by transmitter 908, andcontrols one or more components of mobile device 900.

Mobile device 900 can additionally comprise memory 910 that isoperatively coupled to processor 906 and that can store data to betransmitted, received data, information related to available channels,data associated with analyzed signal and/or interference strength,information related to an assigned channel, power, rate, or the like,and any other suitable information for estimating a channel andcommunicating via the channel. Memory 910 can additionally storeprotocols and/or algorithms associated with estimating and/or utilizinga channel (e.g., performance based, capacity based, etc.).

It will be appreciated that the data store (e.g., memory 910) describedherein can be either volatile memory or nonvolatile memory, or caninclude both volatile and nonvolatile memory. By way of illustration,and not limitation, nonvolatile memory can include read only memory(ROM), programmable ROM (PROM), electrically programmable ROM (EPROM),electrically erasable PROM (EEPROM), or flash memory. Volatile memorycan include random access memory (RAM), which acts as external cachememory. By way of illustration and not limitation, RAM is available inmany forms such as synchronous RAM (SRAM), dynamic RAM (DRAM),synchronous DRAM (SDRAM), double data rate SDRAM (DDR SDRAM), enhancedSDRAM (ESDRAM), Synchlink DRAM (SLDRAM), and direct Rambus RAM (DRRAM).The memory 910 of the subject systems and methods is intended tocomprise, without being limited to, these and any other suitable typesof memory.

In one example, receiver 902 can be similar to a receiving module 202.Processor 906 can further be optionally operatively coupled to ainterference canceling module 912, which can be similar to interferencecanceling module 204, a tone selecting module 914, which can be similarto tone selecting module 206, and/or a channel estimating module 916,which can be similar to channel estimating module 208. Processor 906 canalso be optionally coupled to a channel decoding module 918, which canbe similar to channel decoding module 210, a tone weighting module 920,which can be similar to tone weighting module 212, and/or aninterference estimating module 922, which can be similar to interferenceestimating module 214.

Mobile device 900 still further comprises a modulator 924 that modulatessignals for transmission by transmitter 908 to, for instance, a basestation, another mobile device, etc. Moreover, for example, mobiledevice 900 can comprise multiple transmitters 908 for multiple networkinterfaces, as described. Although depicted as being separate from theprocessor 906, it is to be appreciated that the interference cancelingmodule 912, tone selecting module 914, channel estimating module 916,channel decoding module 918, tone weighting module 920, interferenceestimating module 922, demodulator 904, and/or modulator 924 can be partof the processor 906 or multiple processors (not shown)), and/or storedas instructions in memory 910 for execution by processor 906.

FIG. 10 is an illustration of a system 1000 that facilitatescommunicating with one or more devices using wireless communications.System 1000 comprises a base station 1002, which can be substantiallyany base station (e.g., a low power base station, such as a femto node,pico node, etc., mobile base station . . . ), a relay, etc., having areceiver 1010 that receives signal(s) from one or more mobile devices1004 through a plurality of receive antennas 1006 (e.g., which can be ofmultiple network technologies, as described), and a transmitter 1024that transmits to the one or more mobile devices 1004 through aplurality of transmit antennas 1008 (e.g., which can be of multiplenetwork technologies, as described). In addition, in one example,transmitter 1024 can transmit to the mobile devices 1004 over a wiredfront link. Receiver 1010 can receive information from one or morereceive antennas 1006 and is operatively associated with a demodulator1012 that demodulates received information. In addition, in an example,receiver 1010 can receive from a wired backhaul link. Moreover, thoughshown as separate antennas, it is to be appreciated that at least onetransmit antenna 1008 can be combined with at least one receive antenna1006 as a single antenna.

Demodulated symbols are analyzed by a processor 1014 that can be similarto the processor described above with regard to FIG. 9, and which iscoupled to a memory 1016 that stores information related to estimating asignal (e.g., pilot) strength and/or interference strength, data to betransmitted to or received from mobile device(s) 1004 (or a disparatebase station (not shown)), and/or any other suitable information relatedto performing the various actions and functions set forth herein.

Processor 1014 is further optionally coupled to a RS location receivingmodule 1018, which can be similar to RS location receiving module 302,and/or a scheduling module 1020, which can be similar to schedulingmodule 304. Furthermore, transmitter 1024 can be similar to transmittingmodule 306. Moreover, for example, processor 1014 can modulate signalsto be transmitted using modulator 1022, and transmit modulated signalsusing the transmitter 1024. Transmitter 1024 can transmit signals tomobile devices 1004 over Tx antennas 1008.

In addition, base station 1002 can include a backhaul communicationmodule 1026 for communicating with one or more eNBs 1028 over a backhaulinterface. For example, backhaul communication module 1026 cancommunicate with the eNBs 1028 over a wired or wireless backhaul linkusing one or more backhaul interfaces (e.g., X2 interface in LTE). Wherethe backhaul link is wireless for example, it is to be appreciated thatbase station 1002 can utilize Rx antennas 1006 and receiver 1010 toreceive communications from eNBs 1028, and/or Tx antennas 1008 andtransmitter 1024 to communicate signals to eNBs 1028.

Furthermore, although depicted as being separate from the processor1014, it is to be appreciated that the RS location receiving module1018, scheduling module 1020, backhaul communication module 1026,demodulator 1012, and/or modulator 1022 can be part of the processor1014 or multiple processors (not shown), and/or stored as instructionsin memory 1016 for execution by processor 1014.

FIG. 11 illustrates a wireless communication system 1100 in accordancewith various embodiments presented herein. System 1100 comprises a basestation 1102 that can include multiple antenna groups. For example, oneantenna group can include antennas 1104 and 1106, another group cancomprise antennas 1108 and 1110, and an additional group can includeantennas 1112 and 1114. Two antennas are illustrated for each antennagroup; however, more or fewer antennas can be utilized for each group.Base station 1102 can additionally include a transmitter chain and areceiver chain, each of which can in turn comprise a plurality ofcomponents or modules associated with signal transmission and reception(e.g., processors, modulators, multiplexers, demodulators,demultiplexers, antennas, etc.), as is appreciated.

Base station 1102 can communicate with one or more mobile devices suchas mobile device 1116 and mobile device 1122; however, it is to beappreciated that base station 1102 can communicate with substantiallyany number of mobile devices similar to mobile devices 1116 and 1122.Mobile devices 1116 and 1122 can be, for example, cellular phones, smartphones, laptops, handheld communication devices, handheld computingdevices, satellite radios, global positioning systems, PDAs, and/or anyother suitable device for communicating over wireless communicationsystem 1100. As depicted, mobile device 1116 is in communication withantennas 1112 and 1114, where antennas 1112 and 1114 transmitinformation to mobile device 1116 over a forward link 1118 and receiveinformation from mobile device 1116 over a reverse link 1120. Moreover,mobile device 1122 is in communication with antennas 1104 and 1106,where antennas 1104 and 1106 transmit information to mobile device 1122over a forward link 1124 and receive information from mobile device 1122over a reverse link 1126. In a frequency division duplex (FDD) system,forward link 1118 can utilize a different frequency band than that usedby reverse link 1120, and forward link 1124 can employ a differentfrequency band than that employed by reverse link 1126, for example.Further, in a time division duplex (TDD) system, forward link 1118 andreverse link 1120 can utilize a common frequency band and forward link1124 and reverse link 1126 can utilize a common frequency band.

Each group of antennas and/or the area in which they are designated tocommunicate can be referred to as a sector of base station 1102. Forexample, antenna groups can be designed to communicate to mobile devicesin a sector of the areas covered by base station 1102. In communicationover forward links 1118 and 1124, the transmitting antennas of basestation 1102 can utilize beamforming to improve signal-to-noise ratio offorward links 1118 and 1124 for mobile devices 1116 and 1122. Also,while base station 1102 utilizes beamforming to transmit to mobiledevices 1116 and 1122 scattered randomly through an associated coverage,mobile devices in neighboring cells can be subject to less interferenceas compared to a base station transmitting through a single antenna toall its mobile devices. Moreover, mobile devices 1116 and 1122 cancommunicate directly with one another using a peer-to-peer or ad hoctechnology as depicted. According to an example, system 1100 can be amultiple-input multiple-output (MIMO) communication system or similarsystem that allows assigning multiple carriers between base station 1102and mobile devices 1116 and/or 1122. For example, base station 1102 cancorrespond to apparatus and/or one or more femto nodes described herein,and mobile devices 1116 and 1122 can correspond to apparatus 200 and canthus decode broadcast channels from base station 1102 or in part bycanceling interference from base station 1102.

FIG. 12 shows an example wireless communication system 1200. Thewireless communication system 1200 depicts one base station 1210 and onemobile device 1250 for sake of brevity. However, it is to be appreciatedthat system 1200 can include more than one base station and/or more thanone mobile device, wherein additional base stations and/or mobiledevices can be substantially similar or different from example basestation 1210 and mobile device 1250 described below. In addition, it isto be appreciated that base station 1210 and/or mobile device 1250 canemploy the systems (FIGS. 1-3, 10, and 11), frame structures (FIG. 4),methods (FIGS. 5-8), and/or mobile devices (FIG. 9) described herein tofacilitate wireless communication there between. For example, componentsor functions of the systems and/or methods described herein can be partof a memory 1232 and/or 1272 or processors 1230 and/or 1270 describedbelow, and/or can be executed by processors 1230 and/or 1270 to performthe disclosed functions.

At base station 1210, traffic data for a number of data streams isprovided from a data source 1212 to a transmit (TX) data processor 1214.According to an example, each data stream can be transmitted over arespective antenna. TX data processor 1214 formats, codes, andinterleaves the traffic data stream based on a particular coding schemeselected for that data stream to provide coded data.

The coded data for each data stream can be multiplexed with pilot datausing orthogonal frequency division multiplexing (OFDM) techniques.Additionally or alternatively, the pilot symbols can be frequencydivision multiplexed (FDM), time division multiplexed (TDM), or codedivision multiplexed (CDM). The pilot data is typically a known datapattern that is processed in a known manner and can be used at mobiledevice 1250 to estimate channel response. The multiplexed pilot andcoded data for each data stream can be modulated (e.g., symbol mapped)based on a particular modulation scheme (e.g., binary phase-shift keying(BPSK), quadrature phase-shift keying (QPSK), M-phase-shift keying(M-PSK), M-quadrature amplitude modulation (M-QAM), etc.) selected forthat data stream to provide modulation symbols. The data rate, coding,and modulation for each data stream can be determined by instructionsperformed or provided by processor 1230.

The modulation symbols for the data streams can be provided to a TX MIMOprocessor 1220, which can further process the modulation symbols (e.g.,for OFDM). TX MIMO processor 1220 then provides N_(T) modulation symbolstreams to N_(T) transmitters (TMTR) 1222 a through 1222 t. In variousembodiments, TX MIMO processor 1220 applies beamforming weights to thesymbols of the data streams and to the antenna from which the symbol isbeing transmitted.

Each transmitter 1222 receives and processes a respective symbol streamto provide one or more analog signals, and further conditions (e.g.,amplifies, filters, and upconverts) the analog signals to provide amodulated signal suitable for transmission over the MIMO channel.Further, N_(T) modulated signals from transmitters 1222 a through 1222 tare transmitted from N_(T) antennas 1224 a through 1224 t, respectively.

At mobile device 1250, the transmitted modulated signals are received byN_(R) antennas 1252 a through 1252 r and the received signal from eachantenna 1252 is provided to a respective receiver (RCVR) 1254 a through1254 r. Each receiver 1254 conditions (e.g., filters, amplifies, anddownconverts) a respective signal, digitizes the conditioned signal toprovide samples, and further processes the samples to provide acorresponding “received” symbol stream.

An RX data processor 1260 can receive and process the N_(R) receivedsymbol streams from N_(R) receivers 1254 based on a particular receiverprocessing technique to provide N_(T) “detected” symbol streams. RX dataprocessor 1260 can demodulate, deinterleave, and decode each detectedsymbol stream to recover the traffic data for the data stream. Theprocessing by RX data processor 1260 is complementary to that performedby TX MIMO processor 1220 and TX data processor 1214 at base station1210.

The reverse link message can comprise various types of informationregarding the communication link and/or the received data stream. Thereverse link message can be processed by a TX data processor 1238, whichalso receives traffic data for a number of data streams from a datasource 1236, modulated by a modulator 1280, conditioned by transmitters1254 a through 1254 r, and transmitted back to base station 1210.

At base station 1210, the modulated signals from mobile device 1250 arereceived by antennas 1224, conditioned by receivers 1222, demodulated bya demodulator 1240, and processed by a RX data processor 1242 to extractthe reverse link message transmitted by mobile device 1250. Further,processor 1230 can process the extracted message to determine whichprecoding matrix to use for determining the beamforming weights.

Processors 1230 and 1270 can direct (e.g., control, coordinate, manage,etc.) operation at base station 1210 and mobile device 1250,respectively. Respective processors 1230 and 1270 can be associated withmemory 1232 and 1272 that store program codes and data. Moreover,processors 1230 and 1270 can assist in decoding broadcast channels byselecting, weighting, or classifying certain RS tones, muting RS tonesused by femto nodes, and/or the like.

The various illustrative logics, logical blocks, modules, components,and circuits described in connection with the embodiments disclosedherein may be implemented or performed with a general purpose processor,a digital signal processor (DSP), an application specific integratedcircuit (ASIC), a field programmable gate array (FPGA) or otherprogrammable logic device, discrete gate or transistor logic, discretehardware components, or any combination thereof designed to perform thefunctions described herein. A general-purpose processor may be amicroprocessor, but, in the alternative, the processor may be anyconventional processor, controller, microcontroller, or state machine. Aprocessor may also be implemented as a combination of computing devices,e.g., a combination of a DSP and a microprocessor, a plurality ofmicroprocessors, one or more microprocessors in conjunction with a DSPcore, or any other such configuration. Additionally, at least oneprocessor may comprise one or more modules operable to perform one ormore of the steps and/or actions described above. An exemplary storagemedium may be coupled to the processor, such that the processor can readinformation from, and write information to, the storage medium. In thealternative, the storage medium may be integral to the processor.Further, in some aspects, the processor and the storage medium mayreside in an ASIC. Additionally, the ASIC may reside in a user terminal.In the alternative, the processor and the storage medium may reside asdiscrete components in a user terminal.

In one or more aspects, the functions, methods, or algorithms describedmay be implemented in hardware, software, firmware, or any combinationthereof. If implemented in software, the functions may be stored ortransmitted as one or more instructions or code on a computer-readablemedium, which may be incorporated into a computer program product.Computer-readable media includes both computer storage media andcommunication media including any medium that facilitates transfer of acomputer program from one place to another. A storage medium may be anyavailable media that can be accessed by a computer. By way of example,and not limitation, such computer-readable media can comprise RAM, ROM,EEPROM, CD-ROM or other optical disk storage, magnetic disk storage orother magnetic storage devices, or any other medium that can be used tocarry or store desired program code in the form of instructions or datastructures and that can be accessed by a computer. Also, substantiallyany connection may be termed a computer-readable medium. For example, ifsoftware is transmitted from a website, server, or other remote sourceusing a coaxial cable, fiber optic cable, twisted pair, digitalsubscriber line (DSL), or wireless technologies such as infrared, radio,and microwave, then the coaxial cable, fiber optic cable, twisted pair,DSL, or wireless technologies such as infrared, radio, and microwave areincluded in the definition of medium. Disk and disc, as used herein,includes compact disc (CD), laser disc, optical disc, digital versatiledisc (DVD), floppy disk and Blu-ray disc where disks usually reproducedata magnetically, while discs usually reproduce data optically withlasers. Combinations of the above should also be included within thescope of computer-readable media.

While the foregoing disclosure discusses illustrative aspects and/orembodiments, it should be noted that various changes and modificationscould be made herein without departing from the scope of the describedaspects and/or embodiments as defined by the appended claims.Furthermore, although elements of the described aspects and/orembodiments may be described or claimed in the singular, the plural iscontemplated unless limitation to the singular is explicitly stated.Additionally, all or a portion of any aspect and/or embodiment may beutilized with all or a portion of any other aspect and/or embodiment,unless stated otherwise.

What is claimed is:
 1. A method for muting tones at a first base stationto aid in decoding channels of a second base station in a subframe,comprising: determining a location of one or more tones over which abase station transmits a reference signal; and muting a subset of tonescorresponding to the location of the one or more tones.
 2. The method ofclaim 1, wherein the determining the location comprises determining thelocation of the one or more tones in a subset of subframes over whichthe base station transmits a physical broadcast channel.
 3. The methodof claim 1, wherein the muting comprises muting the subset of tonescorresponding to a plurality of center resource blocks on a subset oforthogonal frequency division multiplexing symbols corresponding to theone or more tones.
 4. The method of claim 1, wherein the mutingcomprises refraining from scheduling a signal transmission over thesubset of tones.
 5. An apparatus for muting tones at a first basestation to aid in decoding channels of a second base station in asubframe, comprising: means for determining a location of one or moretones over which a base station transmits a reference signal; and meansfor muting a subset of tones corresponding to the location of the one ormore tones.
 6. The apparatus of claim 5, wherein the means fordetermining the location is configured to determine the location of theone or more tones in a subset of subframes over which the base stationtransmits a physical broadcast channel.
 7. The apparatus of claim 5,wherein the means for muting is configured to mute the subset of tonescorresponding to a plurality of center resource blocks on a subset oforthogonal frequency division multiplexing symbols corresponding to theone or more tones.
 8. The apparatus of claim 5, wherein the means formuting is configured to refrain from scheduling a signal transmissionover the subset of tones.
 9. An apparatus for muting tones at a firstbase station to aid in decoding channels of a second base station in asubframe, comprising: at least one processor configured to: determine alocation of one or more tones over which a base station transmits areference signal, and mute a subset of tones corresponding to thelocation of the one or more tones; and a memory coupled to the at leastone processor.
 10. The apparatus of claim 9, wherein the at least oneprocessor determines the location of the one or more tones in a subsetof subframes over which the base station transmits a physical broadcastchannel.
 11. The apparatus of claim 9, wherein the at least oneprocessor mutes the subset of tones corresponding to a plurality ofcenter resource blocks on a subset of orthogonal frequency divisionmultiplexing symbols corresponding to the one or more tones.
 12. Themethod of claim 9, wherein the at least one processor configured to mutethe subset of tones is configured to refrain from scheduling a signaltransmission over the subset of tones.
 13. A computer program productfor muting tones at a first base station to aid in decoding channels ofa second base station in a subframe, comprising: a computer-readablemedium, comprising: code for causing at least one computer to determinea location of one or more tones over which a base station transmits areference signal; and code for causing the at least one computer to mutea subset of tones corresponding to the location of the one or moretones.
 14. The computer program product of claim 13, wherein the codefor causing the at least one computer to determine is configured todetermine the location of the one or more tones in a subset of subframesover which the base station transmits a physical broadcast channel. 15.The computer program product of claim 13, wherein the code for causingthe at least one computer to mute is configured to mute the subset oftones corresponding to a plurality of center resource blocks on a subsetof orthogonal frequency division multiplexing symbols corresponding tothe one or more tones.
 16. The computer program product of claim 13,wherein the code for causing the at least one computer to mute isconfigured to refrain from scheduling a signal transmission over thesubset of tones.